Polyamidoamine Dendrimers as Crosslinkers for Efficient Electron Transfer between Redox Probes onto Magnetic Nanoparticles

The efficient conjugation of ferrocenecarboxylic acid (Fc), a usual electroactive probe, onto COOH-modified magnetic nanoparticles (NPs) is reported. Amine crosslinkers were used to couple COOH groups from NPs and from Fc. The coupling efficiencies using different generations of polyamidoamine (PAMAM) dendrimer and ethylenediamine (EDA) were compared through zeta potential measurements, square-wave voltammetry (SWV) and NH2 titration. Highest PAMAM generations led to NH2-modified NPs with increased zeta potential and NH2 density compared to lowest ones. Moreover, no aggregation was observed after crosslinker grafting. SWV was applied to characterize Fc-modified NPs. PAMAM generations 0-3 improved the electrochemical signal in comparison to EDA. However, increasing PAMAM generations led to NPs aggregation. Quantitative results supported the fact that PAMAM generation 0 was the best compromise for large electrochemical signal without NPs aggregation.